Report a Safety Concern
Search

The U.S. Nuclear Regulatory Commission is in the process of rescinding or revising guidance and policies posted on this webpage in accordance with Executive Order 14151 Ending Radical and Wasteful Government DEI Programs and Preferencing, and Executive Order 14168 Defending Women From Gender Ideology Extremism and Restoring Biological Truth to the Federal Government. In the interim, any previously issued diversity, equity, inclusion, or gender-related guidance on this webpage should be considered rescinded that is inconsistent with these Executive Orders.

Home Nuclear Reactors New Reactors Advanced Reactors Who We're Working With Advanced Reactor Application Projects

Long Mott Energy, LLC – Long Mott Generating Station Xe-100 Power Reactor Application

Rendering of Long Mott Generating Station Xe-100 Power Reactor
Who:   Long Mott Energy, LLC
What:   Application for a construction permit for an advanced power reactor
When:   March 31, 2025 (date of application submittal) 
Where:   Calhoun County, Texas
Website:   https://x-energy.com/reactors/xe-100

On this page:

Project Overview

The staff of the U.S. Nuclear Regulatory Commission (NRC) is currently engaged in review activities for the construction permit application from Long Mott Energy, LLC (LME), for the Xe-100 power reactor to be located in Calhoun County, Texas. The Xe-100 project is supported by the U.S. Department of Energy’s Advanced Reactor Demonstration program and would be used to demonstrate the X Energy Xe-100 reactor technology.

Plant Characteristics Description
Reactor Type High-Temperature Gas-Cooled Reactor (HTGR)
Containment Type Functional Containment: Uranium Oxy carbide (UCO) fuel kernel, TRIstructural ISOtropic (TRISO) particle fuel layers, Fuel matrix, Helium pressure boundary, (see SECY-18-0096 for a description of functional containment)
Power Level 4-pack plant with 800 MWth/320 MWe
Fuel Graphite Pebbles with TRISO Particle fuel
Balance of Plant Shared steam powered conversion system (Rankine Cycle)

Key Milestones

Milestones Completion Date
Actual - A
Target - T
Application Tendered 03/31/2025
Acceptance Review
Acceptance Review Start 04/01/2025 – T
Docketing Decision Letter
Issued/Acceptance Review Complete		 05/30/2025 – T
Review Schedule Established/Schedule Letter Issued to Applicant TBD
Safety Review* TBD
Environmental Review* TBD
Hearing TBD
Construction Permit Decision TBD

* The schedule of the key milestones for the safety and environmental reviews will be published once the acceptance review of the construction permit application is completed, and the NRC staff determines if the application can be accepted and docketed for detailed technical review.

Contacts

Contacts for Long Mott Generating Station Xe-100 Power Reactor
Safety Project Managers Adrian Muñiz
301-415-4093
Environmental Project Managers Joe O’Hara
301-415-6854
Public Affairs Officer Scott Burnell
301-415-8204

Page Last Reviewed/Updated Friday, April 4, 2025